Wet-type electric dust collectors have been in practical use as electric dust collectors. In a wet-type electric dust collector, a plurality of electric discharge wires are used as ionizing discharge electrodes. It has been proposed in such a configuration that, when installing these electric discharge wires on a support frame, one end (i.e., the upper end) of the electric discharge wire is elastically supported by means of a plurality of mounting members, for example, with interposing springs or other elastic members, and the other end (i.e., the lower end) is fastened on an electrode bar which extends horizontally from the support frame.
The electrode bar and the electric discharge wires are made of HASTELLOY when used in an environment of high temperature and a corrosive or oxidizing atmosphere.
HASTELLOY is an alloy containing Ni-Cr-Mo as main components, and HASTELLOY C-276, in particular, is employed in applications which require durability to high temperatures and corrosion or oxidation.
When ends of the electrical discharge wires are fastened on the electrode bar by welding, a difficulty arises because the electrical discharge wires cannot be changed. In practical use, this technique utilizes one end of an electric discharge wire inserted in a set hole made in the electrode bar, and the end of the electric discharge wire is bent. The bent portion of the wire is engaged in the set hole by housing it in a set seat formed by enlarging the bottom half of the set hole, thereby fastening the electric discharge wire. In this case, there is a minute clearance, or gap, between the electric discharge wire and the set hole of the electrode bar, or between the bent end portion of the electric discharge wire and the set seat in the electrode bar, and a minute clearance can arise in a portion of linear contact due to vibrations or the like, thereby causing a potential difference in the minute clearance when the electric discharge wire discharges. This results in electrical wear of the material.
Use of HASTELLOY as the material of construction for the electrode bar and the electric discharge wire also contributes to this problem because the high hardness of the HASTELLOY makes it difficult to bring the bent portions of the electric discharge wires and the set holes in close contact without a clearance.